The present invention relates to a tape drive, and more specifically to a method of reducing the power consumption of a buffer in a tape drive.
File systems such as a Linear Tape File System (LTFS) often use tape drives. In tape drives, data that is sent from a host during writing, and data that is read from a tape during reading are stored in a buffer. According to various embodiments, these bits of data in the buffer are written to the tape sequentially during writing, and transferred to the host sequentially during reading.
The data transfer rate (hereinafter called “tape transfer rate”) required to write data to the tape or read data from the tape must be equal to the data transfer rate from the host or to the host (hereinafter called “host transfer rate”). This is because the amount of data in the buffer varies according to the relationship between the tape transfer rate and the host transfer rate and thus there is a need to keep the transfer rate of data to the host or from the host the same.
The size of the buffer described above is designed based on the maximum tape transfer rate supported by the tape drive. However, in most cases, the host transfer rate is less than half of the maximum tape transfer rate in an actual environment. In other words, the size of the buffer often has a sufficient amount of available room to read and write data via the host. Therefore, part of the buffer can be left unused according to the host transfer rate. Freeing up a portion of the buffer desirably conserves power of the buffer.
Japanese Patent Application Publication No. 2005-303458 discloses a communication apparatus that stores data in a buffer memory before transmitting, or after receiving the data. Furthermore, according to Japanese Patent Application Publication No. 2005-303458, the size of a data buffer for storing data is determined based on information on the data input/output rate when data is input to or output from the buffer memory.
U.S. Pat. No. 8,145,932 discloses that when the usage of an Information Handling System (IHS) such as a server is low, a Redundant Array of Independent Disks (RAID) controller selected on a storage network is switched to a power saving mode.